Water clarification is well-known throughout a number of industries. Various physical means have been used to remove particulate matter dispersed in a bulk liquid phase. Examples of common particulate separation techniques include filtration, settling, desalting, electrochemical techniques, centrifugation, flotation and the like. Such separation processes can often be made more efficient by the use of coagulating and flocculating agents. Wastewater containing emulsified oil can be difficult to treat by physical processes alone. In such circumstances, demulsifying coagulants and flocculants can be used to break the emulsion and hasten agglomeration of the oil particles formed. Inorganic coagulants alone or in combination with organic polyelectrolytes have been used in demulsification. However, these treatments are not completely satisfactory because they increase solids content, which can cause sludge disposal problems.
Tannins are astringent water-soluble extracts from the bark, pods, leaves, and fruit of various plants and trees. Established industrial practices of extracting tannins from the wood of the quebracho tree and the bark of the wattle tree have made condensed tannins available in substantial quantities. Condensed tannins are polyphenolic and polymerize in combination with other chemicals such as formaldehyde.
U.S. Pat. No. 4,558,080 discloses the production of stable tannin-based flocculants made by polymerizing tannin with an aldehyde such as formaldehyde and an amino compound, such as monoethanolamine, while monitoring the viscosity of the reacting mixture.
U.S. Pat. No. 4,734,216, discloses a flocculating compound comprised of polymerized tannin described in the above referenced patent in combination with an inorganic flocculant such as aluminum sulfate or iron chloride.
U.S. Pat. No. 5,643,462 discloses a composition comprised of a water soluble/dispersible tannin containing polymer obtained by polymerizing ethylenically unsaturated monomers with tannin, the method of preparing the same and their use for water clarification.
U.S. Pat. No. 6,478,986 teaches a process for the production of a quaternary tannate as a coagulating/flocculating agent, and its use for treating drinking water and water used in industry. The coagulating/flocculating agent is a vegetable polyelectrolytic cation.
There still remains a need for a simple preparation of tannin based environmentally friendly polymeric coagulants, which are useful in water clarification processes.